Simulation of Lightning Protection for Composite Civil Aircrafts

Transcription

1 Available online at Procedia Engineering 17 (2011) The 2nd International Symposium on Aircraft Airworthiness (ISAA 2011) Simulation of Lightning Protection for Composite Civil Aircrafts ZOU Tianchun a *, WANG Jin a, MAO Keyi a, FENG Zhenyu a Civil Aircraft Airworthiness Certification Technology and Management Research Center, Civil Aviation University of China, Tianjin , China Abstract Lightning damage will be a hazard to composite aircrafts if they are not properly designed. In this paper, based the aircraft lightning protection theory, lightning zoning and its protection technology for a certain type of composite civil aircraft are studied utilizing EMA3D electromagnetic simulation software, which can provide relevant information for design and verification of lightning protection for civil aircrafts Published by Elsevier Ltd. Selection and/or peer-review under responsibility of Airworthiness Technologies Research Center NLAA, and Beijing Key Laboratory on Safety of Integrated Aircraft and Propulsion Systems, China Open access under CC BY-NC-ND license. Keywords: Composite materials; Lightning protection; Lightning zoning; Simulation 1. Introduction Nowadays, composite materials are widely applied in civil aircrafts. Composite aircrafts are more vulnerable to lightning than traditional metal aircrafts [1]. When lightning strike occurs, the composite aircrafts cannot be well out of the lightning current conduction, which cause great security threat to the flight of the civil aircrafts. Therefore, it is significant for composite aircrafts to protect from lightning. There are mainly two means to test the safety of aircraft. One is physical test and the other is simulation. Currently the main means for lightning protection research is physical test interiorly. However, * Corresponding author. Tel.: ; fax: address: zoutianchun@yahoo.com.cn Published by Elsevier Ltd. doi: /j.proeng Open access under CC BY-NC-ND license.

2 ZOU Tianchun et al. / Procedia Engineering 17 (2011) its high investment and high-risk characteristics bring us a lot of inconvenience. Therefore, it is in dire need of carrying out the simulation of lightning protection [2, 3]. Lightning zoning is the basis for aircraft lightning protection. This paper will use the aircraft lightning protection theory as a guide, based on electromagnetic simulation platform to study a certain type of composite civil aircraft lightning zoning and its protection technology, which can provide relevant information for design and certification of lightning protection for civil aircrafts. 2. Lightning Zoning and Its Current 2.1. Lighting zone Lightning strikes do not reach all aircraft surfaces. The intensity and duration of currents entering those surfaces may be vary according to their location. Lightning strike zones have been defined to account for these variations. Once the locations of these zones have been established for a particular aircraft, the lightning environment and protection need can be determined. The locations of these zones on any aircraft are dependent on the aircraft's geometry and operational factors, and often vary from one aircraft to another. Zone 1 is defined as the initial attachment point, so airplanes extremities should be considered within the direct strike zone. Those forward extremities or leading edges should be considered within zone 1A (low possibility of lighting arc channel hang-on), and extremities that are trailing edges should be within zone 1B (high possibility of lighting arc channel hang-on). Surfaces directly after zone 1A should be considered as zone 2A, which is a swept stroke zone with low possibility of lightning arc channel hang-on. Generally, zone 2A will extend the full length of the surface after zone 1A. Trailing edges of surfaces aft of zone 2A should be considered zone 2B, or zone 1B if initial attachment to them occurs. Surfaces of the vehicle for which there is a low possibility of direct contact with the lightning arc channel that are not within any of the above zones, but which lie between them, should be considered as within zone 3. Zone 3 areas may carry substantial amounts of electrical energy. Figure 1 shows the lighting strike zones of airplane. For almost conventional designed airplanes, the fuel tank is located within zone 2A and zone 3. ZONE 2B ZONE 2A ZONE 1B ZONE 1A ZONE 3 Fig. 1. Lighting strike zones (typical)

3 330 ZOU Tianchun et al. / Procedia Engineering 17 (2011) Lighting current There are four current components (A, B, C, and D) applied to determine direct effects. Current waveform E is used to determine indirect effects. Components A, B, C, and D each simulate different natural lighting current characteristic and are shown in figure 2. They are applied individually or as the combination of two or more components together in one test [2]. Fig. 2. Current waveforms Component A represents the initial high peak current. It has a peak amplitude of 200kA (10 percent) 2 and an action integral ( i dt ) of (20 percent) with a total time duration not exceeding. Component B represents the intermediate current. It has an average amplitude of 2kA (l0percent) flowing for a maximum duration of 5ms. Component C represents the continuing current. It transfers a charge of 200 coulombs (20 percent in a time of between 0.25 and 1 second). Component D represents the restrike current. It has a peak amplitude of 100kA (+10 percent) and an action integral of (20 percent). This component may be either unidirectional or oscillatory with a tota1 time duration not exceeding. 3. Simulation Analysis of An Aircraft Lightning Zoning 3.1. The establishment of composite aircraft model and lightning enviroment CADfix has a common pre/post processors, the preprocessor can form necessary structures and grid before the solution. And it can transform a variety of common MCAD software interface (such as CATIA, UG, etc.). It can define model materials and its electromagnetic parameters, excitation and output requirements. Using CADfix to establish a certain type of civil aircraft model, and set the plane wave excitation (Figure 3). This model is posited the coordinates: x-axis is parallel to the axis of the aircraft wing, y-axis is parallel to the frame axis, and z-axis is perpendicular to them. The model size is inches (length width height). It was split to the units. A current component was selected in this paper as a plane wave excitation. The peak amplitude of it is 200KA, and duration of 500μs. A current component was injected along with the Y-axis direction at 45

4 ZOU Tianchun et al. / Procedia Engineering 17 (2011) angle (ie, after the top of the body) into the aircraft. Thereby we established the aircraft lightning electromagnetic environment. Fig. 3. Aircraft model and the excitation source The A component lightning current entered into the after of the top of the frame. And we used Matlab to simulate A component s time-domain waveform, which was shown in Figure 4 as the form of A waveform diagram. The peak current is near 200KA at about 5μs, according to the theoretical analysis before Current(KA) KA Microseconds Time(Microsecond) Fig. 4. A current s time-domain waveform The above aircraft model and plane wave excitation source were the object of this research and its external lightning environment respectively Results

5 332 ZOU Tianchun et al. / Procedia Engineering 17 (2011) Model calculation was based on EMA3D electromagnetic simulation platform, from which the lightning attachment points on the aircraft at different times after the strike, and the peak induced electric field from lightning at the surface of aircraft during this time can be got(figure 5 and Figure 6) Electric field(v/inch) E(v/inch) t(ns) Time(Nanosecond) Fig. 5. The time-domain distribution of the aircraft lightning attachment The graph told us the changes of induced electric field on aircraft surface. From 0 ~ 300ns, the induced electric field increased from 0 to 3.575E +5. At the moment the lightning current has almost been conducted to the head of aircraft (Figure 5).

6 ZOU Tianchun et al. / Procedia Engineering 17 (2011) Fig. 6 The peak induced electric field It shown the induced electric field was gradually increased within the first 300ns, and almost transmit all over the aircraft surface. Therefore, we calculated the peak electric field within the first 1.25μs, which was 1.772E +6. It was the top electric field that lightning current induced on the surface of the aircraft (Figure 6). 4. Conclusions The lightning electromagnetic environmental effects simulation results above can be explained as follows. This excitation source is the direction of the top rear of the aircraft, so the more serious lightning attachment area is the wing tip and the tail end. This is consistent with the theoretical basis for this article. According to the simulation results, not only the length of time in that lightning current spread for this composite aircraft, but also the largest induced electric field data on the aircraft during this period can be seen. The simulation results can provide relevant information to lightning protection design and verification for composite civil aircraft and its physical tests. Modern aircrafts are increasingly using composite materials instead of metal. Composite materials reduce the aircraft's structural weight, but reduced the original metal body s electromagnetic shielding efficiency, so the composite aircraft structures performance to against lightning should cause enough attention of the industry. As traditional means of experimental tests with high-cost, high-risk defects, lightning protection of composite aircraft gradually become to pay attention to both simulation and physical testing. In this article, the EMA3D electromagnetic simulation software was used, which can effectively simulate lightning electromagnetic environmental impact for composite aircraft. It can provide some technical support to lightning protection research for composite aircrafts. Acknowledgements This work was supported by the science and technology item from Civil Aviation Administration of China (No. MHRDZ201010). References [1] Niu Chunyun. Aircraft design and manufacture of composite structures [M]. Xi'an: Northwestern University Press, 1995.

7 334 ZOU Tianchun et al. / Procedia Engineering 17 (2011) [2] SAE Committee AE4L, Lighting Test Waveforms and Techniques for Aerospace Vehicles and Hardware[R], Report of SAE Committee AE4L, 1978: [3] Fisher F A., J. Plumer A,.Perala RA, Lightning Protection of Aircraft [M], Lightning Technologies Inc., 2004.